I have used this site in the past, but be careful: especially regarding metal, it has been known to churn out all sorts of inane associations. If you type in Darkthrone, you might occasionally get Lamb of God or Sum 41.

Reality is that services on the internet are integrating social aspects to bring in revenue and maintain people's interest within that environment. It works. Kinda like how ANUS has these forums. Nobody forces us to participate, so that's not really a valid argument...

If Last.fm sucks, it is because it is not well thought out. As an example look up "Absurd" and every artist with that name is thrown on one page with no distinction. There is no clear organization of albums and tracks, all that matters is what tracks are the most popular with the masses. And there is seemingly no authority, no moderation.

RateYourMusic is infinitely more useful and better organized. All users are rated on musical compatibility with eachother, and after some time you can get weighted suggestions from this. It is a good resource to look up details on albums and artists, and while anyone can contribute, there is a formal structure to be followed.